Adsorption of copper ion from its aqueous solution by a novel biosorbent Uncaria gambir: Equilibrium, kinetics, and thermodynamic studies

In this paper, gambir was chemically modified into insoluble adsorbent (GA). The GA was characterized by FTIR, pHzpc, SEM, and BET. The effects of pH, adsorbent dosage, initial concentration of Cu2+ solution and contact time were studied. Batch experiments were performed with aqueous copper solutions of concentration 10 mg/L, at pH 5.0 and 0.30 g adsorbent. The experimental data was analyzed using pseudo-first order, pseudo-second order and Elovich kinetic models. The correlation coefficient calculated from pseudo-second order equation was higher than pseudo-first order and Elovich kinetic equations, indicating that equilibrium data fitted well with pseudo-second order model where adsorption process was chemisorptions. The adsorption equilibrium was well described by Langmuir isotherm model. The maximum adsorption capacity was found to be 9.950 mg/g at 333 K. The Gibbs free energy change, ΔG°, values were negative indicating that the process of Cu2+ ions adsorbed onto GA was spontaneous. The positive values of ΔH° and ΔS° suggested that the process of adsorption was endothermic at high temperature.